Submerged drain cooler in evaporators



Dec. 13, 1927.

R. C. JONES SUBMERGED DRAIN COOLER IN EVAPORATORS Filed July 24. 1924 INVENTOR ATTORNEY Patented Dec. 13, 1927. 1

UNITED STATES I 1,652,204 PATENT OFFICE.

R'lj'SSELL G. JONES, F IBRONXVILLE, NEW YORK, ASSIGNQR TO THE GRISCOM-RUSSELL I COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

SUBMERGED DRAIN COOLER IN EVAiPORATORS.

Application filed July 24,

The present invention relates to steam generating systems and has to do particularly with the construction and operation of evaporators in a steam generating system with particular reference'to the disposition of the hot drains from the heating coils of the evaporators sothat the available heat in such drains may be advantageously used in the system.

Raw water ordinarily available. for use in steam generating plants contains undesirable impurities to such an extent that the water must be treated to remove such impurities before it can be successfully used 5 in the boilers. For this'reason the impure raw water is usually distilled in evaporators provided for the purpose and the purified output employed as the boiler feed water.

The heat for effecting the evaporation of the impure raw water is commonly derived from steam drawn from the boilers and condensed in the heating element of the evaporator as heating medium therefor. The purified vapor output of the evaporator is drawn ofi and condensed, and the condensate is then passed on to the boiler to supply the necessary -makeup requisite to the operationof the system. When the requirements of the system demand that more than one evap orator be employed, it is common practice to install two or more evaporators as needed, to arrange for supplying heating steam to the first evaporator directly from the. boilers, and to utilize as heating medium for each succeeding evaporator, the vapor output of the preceding unit. I

The available heat contained in the evaporator vapor output and in the hot drains issuing from the heating elements of the evaporator units must'be utilized in the systern in order to avoid heat losses. The heat is usually conserved by passing these hot returns into heat exchanging relation with the boiler. feed. water, and thus preheating the water before its admission to the boilers.

The evaporator coil drains are commonly discharged from the evaporating unit at a relatively high pressure and thus represent a considerable amount of available heat. In

order to effect discharge of condensate from the evaporatorheating elements, a trap is provided in conjunction with each heating element andfunctions to permit discharge of condensate from the element and at. the

same time to prevent escape of uncondensed 1924. Serial no. 728,039.

sures considerably above atmospheric.

In a .system employing more than one evaporator, it has also been proposed to discharge the cnil drains from the evaporators into a region of reduced pressure corresponding to the pressure of the vapor discharged from the last efi'ect evaporator,

whereupon the excess of sensible heat in the coil drains corresponding to the pressure existing in the 0011s over that corresponding .to the pressure into which the coil drains are discharged, will produce a vaporizing or flashing action and will thus convert a portionof the discharged condensate into steam. Coil drains from 'an evaporator may also be reduced to the pressure of the vapor output of that evaporator, and the quantity of resulting flash steam may be joined with thevapor output and used as heating mediuin for the succeeding evaporator. These arrangements are open to the objection of high initial cost of installation, difliculties of operation. and regulation. due to an increased number of operating units, and the like. It has also been proposed to condense the coil drains from the heating elements of the evaporators in the boiler feed heater without the intermediate use of a trap, the object of this arrangement being to eliminate the problem of operating and regulating the trap. In these installations, the heat exchanger which receives the coil drains must be of ample capacity to insure complete condensation of all steam-admitted to it in order to prevent heat loss by steam blowing thru the heat exchanger uncondensed.

It is a principal object of this invention to provide an evaporator system which effects the disposition of the drains from the heating elementsof the respective evaporator units and the utilization of the available relation with the fluid in the evaporating space of the respective evaporator units. The coil drains from each evaporator unit are passed 1nto heat transferring relatlon with the liquid undergoing evaporation in that unit. The inventionfurther contemplates passing the coil drains from each evaporator unit into heat exchanging relation, not only with the liquid undergoing treatment in that unit, but also with the liquid being evaporated in succeeding units operating at successively lower )ressures. In this way, the available heat in he drains from each evaporator unit is abstracted in a succession of steps at decreasing pressures and temperatures. A trap is preferably provided in connection with the heating element of each unit to prevent passage of uncondensed heating steam thru the elements.

'It is also an object of the invention to provide for the heat transfer between the coil drains and the liquid undergoing treatment by means of a rugged, inexpensive heatex changer contained entirely within the evaporator unit itself and also designed to facilitate removal of scale which may accumulate upon the heat transferring sur faces of the unit. These heat exchangers for accom-' modating the coil drains are so arranged in reference to the principal heating elements of the evaporator units that they may be treated for the removal of scale deposits at the same time and by the same operation by which removal of scale fromthe main heat ing elements is accomplished.

I have illustrated a preferred embodiment of my invention in the accompanying drawings, in which Figure 1 is an elevational view showingan evaporator embodying my invention; Figure 2' is an elevational view showinga system embodying my invention wherein two evaporating effects are employed; and Figure 3 is a similar elevational view showing a modification.

The evaporator consists of a shell 1 for containing the liquid under treatment and a suitable heating element 2 disposed within the shell 1 for the purpose of effecting vaporization' of the liquid in-the shell. The

heating element 2 commonly consists of a suitable arrangement of heat transferring tubing submerged in the liquid in the shell 1 and receiving thru line 3 asupply of -heat' ing steam from the main boilers or from another suitable source. The heating element 2 here shown consists of a .plurality of vertically disposed helical .coils extending between inlet manifolds 4: provided for the purpose of distributing the incoming steam to the respective coils, and discharge manifolds 5 provided for the purpose of receiving the fluid discharged from the coils and passing it out of the apparatus. A trap 6 is connected tothe discharge manifolds 5 and serves to permit discharge of condensate from the heating element and at the same time to prevent discharge of uncondensed steam. The vapor arising from the liquid in the shell 1 passes up thru the steam dome 7 of the evaporator and is discharged thru the vapor outlet line 8, whence it is disposed of as desired. The vapor output is commonly passed into heat exchanging relation with the boiler feed water in order to preheat the water before its admission to the boilers.

The invention contemplates transfer of heat from the condensate discharged from the heating element 2 to the water within the shell 1. To this end, a heat exchanger 9 is built into the evaporator shell 1 at, a point near the bottom of the shell. The con densate passing the trap 6 is conveyed directly into the heat exchanger 9 which may be at any desired pressure lower than that in coil 2, and during the passage of the condensate thru this heat. exchanger ample opportunity is afforded for transfer of heat to the liquid in the shell 1. In order to prolong the length of time during which the heat transfer from the condensate to the liquid within the shell takes place, the heat exchanger 9 is divided bymeans of partitions 10 and 11 into three passes so that the teon'densate will traverse the length of the heater three times before it is finally discharged thru line 12 and passed into heat transferring relation with the boiler feed water, or'is otherwise disposed of. These partitions are arranged in headers 13 and 14 provided at the respective cndsof the tubes constituting the heat exchanger. During this prolonged period of heat transfer. the temperature of the coil drains passing the trap 6 will be reduced to substantially the temperature of the liquid under treatment in shell 1, with the result that a considerable economy in operation is effected.

The liquid being evaporated may contain a considerable amount of scale forming impurities and the invention contemplates construction of ,the heat exchanger 9 in such fashion that scale accumulating on the heat transferring surfaces may readily be removed. To this end, the headers 13 and 14 are rigidly secured to the evaporator shell 1 and are thus maintained at a fixed distance apart. Th peat transferring tubes of the heat exchanger 9 are rigidly secured at their respective ends in the headers 13 and 14 and are slightly bowed, so that upon changes in temperature with resulting longitudinal expansion or contraction of the tubes, the amount which they are bowed will vary, and thereby cause a flexure of the tubes which will effectively loosen and crack off accumulated scale deposits. The requisite change in temperature for effecting scale removal is produced by passing hot Water and cold water successively thru the heat transferring tubes. The heat exchanger 9 is connected in series relation'with the main heating element 2 of the evaporator and,

since the heating element 2 is usually ar-' ranged for accomplishing scale removal by subjecting the element to abrupt temperature changes, scale removal from both the heating element 2 and the heat exchanger 9 may be effected at a single operation by passing 4 hot and cold fluid successively thru the respective heat exchangers in series arrange ment.

The present invention is applicable equally well to a system employing a single evaporating unit or effect and to a system employing more than one unit. A system employing two evaporating units is shown in Figure 2. Vapor from the first effect evaporator is passed thru line 8 into the heating element 2 of the second effect and serves as heating medium for effecting evaporation in the second evaporator 1. A heat exchanger 9 and trap 6- are provided for handling drains f om the heating element 2 of the second e ect and transferring heat from such drains to the Water in shell 1". The discharge line 12 conveying the drains issuing from the heat exchanger 9 is joined with the discharge from the trap 6 of the'second effect evaporator and the heat exchanger t) therefore receives not only the coil drains from the heating element 2 but also the drains issuing from the heating element 2 of the first effect evaporator. In this fashion, the drains from the first effect are passed successively into beat transferring relation with the liquid undergoing evaporation in the first effect and the liquid undergoing evaporation in the second effect. If. more than two evapqrating units are employed, this system is carried out so that the coil drains from each effect are first passed into heat exchanging relation with the liquid undergoing evaporation in that effect and are then successively passed into heat transferring relation with a the liquid under oing evaporation in each of the succeeding e ects. 4

ImFigure 3 I have illustrated an arrangement in which the auxiliary heat exchanger 9 is'positioned vertically in the evaporator shell. This arrangement may be of advantage in certain installations and partieularly results in placmg the heat ex-' the case when the heat exchanger 9 is located in the bottom of the evaporator shell. A discharge line from the trap'G is passed into the upper end of the heat exchanger 9, the excess pressure in the coils 2 being ample to produce the fiowfrom the trap into the heat exchanger 9.

\Vhile-I have herein illustrated only pre ferred embodiments of my invention, certain changes and modifications in construction and arrangement may be made within the scope of the appended claims.

I claim: I v

1. In a steam generating system, a series of evaporators, each evaporator having a closed heating element therein, said evaporato'rs being operable at successively lower pressures for supplying purified Water vapor, means for supplying steam at relatively high pressure to the heating element of the first evaporator of the series, means for passing the drains from said heating element into the evaporating space of that evaporator, and I means for passing said drains into heat exchanging relation with the liquid in the evaporator space of the next evaporator operable at lower pressure. I

2. In a steam generating system, a series of evaporators, each of said evapora'tors having a closed heating element therein, said evaporators being operable at successively --lower pressures for supplying purified water vapor, means for suppl ing steam to the heating element of the first "of said evaporators, means for passing the drains from said heating element into heat exchanging relation with the liquid under treatment in Dthfat evaporator, and means for passing said drains into heat exchanging relation with the li uid in the evaporatin space of the succeeding evaporator operable at a lower pressure.

3. In asteam generating system, a series of evaporators, each of said evaporators having a closed heating element therein, said evaporators supplying purified-water vapor, means for suppl ing steam to the heating element of the rst evaporator, means for supplying to each succeeding evaporator as heating medium therefor the vapor output of the preceding evaporator, and means for passing the drains from each evaporator into heat exchanging'relation with the liquid being evaporated therein.

4. In a steam generating system, a series ing a closed heating element therein, said evaporator-s supplying purified Water vapor,

means for supplying steam to the heating elementof the first evaporator, means for supplying to each succeeding evaporator as heating medium therefor vapor from the preceding evaporator, means for passing the drains from each evaporator into heat exchanging relation With the liquid being evaporated therein, and means for joining the drains from each evaporator heating element with the condensatefrom the preceding elements and passing said joined fluids into heat exchanging relation with the fluid in the evaporating space of said evaporator.

6. An evaporator comprising a shell for containing liquid under treatment, a closed heatin element in said shell for conducting steam lnto heat transferring relation with said liquid to effect vaporization thereof, a trap for receiving the drains discharged from the heating element and preventing escape of uncondensed steam, and a heat exchanger within said shell for receiving the fluid issuing from said trap and transferring heat therefrom to the liquid under treatment, said heat exchanger comprising a plurality of longitudinally flexible tubes having fixed ends, whereby changes of contion with said liquid to effect vaporization thereof, a trap for receiving the drains discharged from the heating element and preventing escape of uncondensed steam, and a heat exchanger within said shell for receiving the fluid issuing from said trap and transferring heat therefrom to the liquid under treatment, said heat exchanger comprising a plurality'of slightly'bowed tubes having rigid end supports whereby the curvature of said tubes will vary upon changes in temperature to thereby lated scale.

8. In a steam generating system, a series of evaporators operable at successively lower pressures, each of said evaporators having a closed heating element therein, said exfoliate accumuevaporators supplying purified water vapor,-

means for supplying steam at relatively high pressure to the heating element of the first evaporator, means for withdrawing the drains from said heating element and reducing the pressure thereon, means for passing said drains into heat exchanging relation with the liquid undergoing treatment in said evaporator, meansfor joining said drains at said reduced pressure with the coil drains from a succeeding evaporator, and means for passing said joined drains into heat exchanging relation With the liquid undergoing treatment in the evaporators operable at pressures lower than that at the first evaporator.

In testimony whereof I affix my signature.

. RUSSELL C. JONES 

